WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 6Citation - Scopus: 8Dehydration, Water Vapor Adsorption and Desorption Behavior of Zn[b3o3(oh)5] · H2o and Zn[b3o4(oh)3](Taylor and Francis Ltd., 2012) Alp, Burcu; Gönen, Mehmet; Atakul Savrık, Sevdiye; Balköse, Devrim; Ülkü, SemraThe dehydration behaviors of two different hydrated zinc borate species, Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3], which are industrially important flame retardants, were studied by thermal gravimetric(TG) analysis and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Dehydration onset temperatures of Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3] were 129 and 320°C, respectively, at a 10°C/min ramp rate. A very small amount of boric acid was volatilized in addition to water vapor when both samples were heated at 250°C. A significant amount of water vapor was adsorbed by Zn[B3O3(OH)5] · H2O from air at 25°C. However, Zn[B3O4(OH)3] adsorbed a very small amount of water under the same conditions. Both zinc borates did not have a tendency to cake during storage.Article Citation - WoS: 13Citation - Scopus: 14Characterization and Dehydration Behavior of a Natural, Ammonium Hydroxide, and Thermally Treated Zeolitic Tuff(Taylor and Francis Ltd., 2011) Narin, Güler; Balköse, Devrim; Ülkü, SemraAqueous NH4OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), volumetric N2 adsorption at -196°C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH4OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite.Changes in the infrared bands corresponding to vibrations of the O-H and N-H bonds upon in situ heating under vacuum were analyzed.Article Citation - WoS: 17Citation - Scopus: 23Synthesis of Zinc Borate by Inverse Emulsion Technique for Lubrication(Springer Verlag, 2011) Atakul Savrık, Sevdiye; Balköse, Devrim; Ülkü, SemraLubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na2B4O7·10H 2O) and zinc nitrate (Zn(NO3)2·6H 2O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600 °C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50 °C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as -3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.Article Citation - WoS: 30Citation - Scopus: 35Effect of Temperature and Time on Zinc Borate Species Formed From Zinc Oxide and Boric Acid in Aqueous Medium(American Chemical Society, 2007) Eltepe, H. Emre; Balköse, Devrim; Ülkü, SemraThe effect of temperature and time of heating of zinc oxide and boric acid in aqueous medium on product type, dehydration behavior, crystal morphology, and structure was investigated for the production of flame retardant and smoke suppressant zinc borate. Two different products dehydrated at 140 and 350°C were obtained and characterized by thermal gravimetric analysis, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy.Article Citation - WoS: 10Citation - Scopus: 11Use of Clinoptilolite in Ethanol Dehydration(Taylor and Francis Ltd., 1996) Tıhmınlıoğlu, Funda; Ülkü, SemraClinoptilolite-type natural zeolite, which exists in various regions of Turkey, has been experimentally studied. For the ethanol-water-local clinoptilolite system, uptake and breakthrough curves were determined under a nitrogen gas atmosphere. In adsorption kinetics and adsorption equilibrium studies, the effects of particle size, temperature and, amount of zeolite on the uptake rate have been investigated. The breakthrough curves for four different flow rates of ethanol and three different bed heights were determined in dynamic column studies. The results of the experiments show that intraparticle diffusion is the main resistance. The local clinoptilolite is a promising adsorbent for water adsorption from aqueous ethanol.